Question

7. MECHANISM Using electron push arrows, provide a logical, detailed, stepwise mechanism for the following transformation. Be sure to show each step in the mechanism, including initiation, and propagation steps as well as at least one termination step. HBr → Br ROOR

Answer 1

It is peroxide effect Lantim arkonikoff's rule. i) There are three steps o curs. © Initiation - It require only any one of radicle generator. hydrogen peroxide or organic peroxide that is R-o-o-R. The alkyl peroxide when expose to UV light or heat undergoes homolytic cleavage to generate two alkyloxy radicle. (QR-0) @ R- ö-ö R 2 -R-o. DH = + ISOKJ) homolytic cleavage mo BR-o +H. Br: R- ö-H + Br: This step is exothermic and low activation Energy. The alkoxy radicle pickup hydrogen from H-By to give bromine radicle that is ready to react with unsymmetricle alkene (Prop--ene)

6 propogation - The bromine radicle can attached itself from either side of double bond but it choses to add from 2 radicle species. The radicle is considered an electron deficient species. stability ordert 3° > 2° > ° > CH3 2 radicle pickup H from bromoalkone (1 bromo propane) It also generate a new bromine radicle that will propogate the chain reaction by continuing these two step till reaction reaches to termination step. CH3 -CH=CH2 + Bri- CH3 -CH -CH2 (less stable) two site for bromine attachment CH3-CH-CH2-By z radicle. more Stable H @ Chech-CH₂-By th-Br + CH₃-CH-[H₂-Br + By: first step propogation is bromine radicle attachment second step prop" hydrogen radical .

© Termination - The reaction discontinue when free radicle species exhausted by any one of following step. t : Br. t. Br: Brz Bromine - h Chz-CH-CH2-BY Cityn CH - CH2-By CH₃-CH-th, Br cz - ch-CH2-By ③ CH3 -CH-CH₂-Br + Br - cr3-ch -CH₂-By 1,2 dibromo propane.